This invention relates to a multi-piece vehicle wheel assembly, and more specifically, to a wheel assembly incorporating a lightweight, reduced-mass aluminum alloy rim. The invention eliminates excess mass and inertia in an optimal multi-piece wheel construction applicable for both motor sport and normal road use.
In an effort to create the optimal wheel, design engineers utilize complex computer simulations and expensive equipment to form a precisely accurate and highly efficient multi-piece structure. The optimal design must account for every gram of weight in the wheel as each gram generates extreme levels of force at high speeds. Moreover, because vehicle performance is improved by reducing both the wheel mass and its rotational inertia, it is especially advantageous to remove inessential mass from the rim of the wheel. The further away a given mass is removed from the wheel centerline, the greater the reduction in wheel inertia.
Although aluminum alloy wheels are now fitted to the majority of vehicles, up until recently steel wheels were more common. While most alloy wheels are one-piece there are several classes of multi piece alloy wheels, including those that use the same construction path as all steel wheels. This invention concerns the specific class of alloy wheels wherein a wheel center is attached to a wheel rim. There are multi-piece and one-piece rim constructions in use where the rims have bolt holes through their flanged regions, and the wheel center and rim(s) are fastened together with screws/bolts and nuts, or similar function rivets. There is also a related class of rims which feature blind holes for fastening the center with tap screws/bolts. This invention is particularly applicable to this last category of rims and the wheels made with them.
FIGS. 1A, 1B, and 1C illustrate a conventional two-piece wheel construction “W” of the prior art. This particular wheel style is currently produced for OEM applications in vehicles, such as manufactured by BMW®, as well as AM applications for car enthusiasts. The wheel “W” includes a wheel center “C” and rim “R” joined together by suitable fasteners “F”. The fasteners “F” extend through an outer margin of the wheel center “C” and penetrate respective blind fastener holes “H” formed with an inside major surface of the rim “R”. As best shown in FIG. 1C, the rim “R” has a much thicker annular mass in an area “T” of the fastener holes “H” as compared to the area “T′” of rim “R”. This added mass increases the weight of the rim and reduces the overall performance of the assembly as compared to conventional one-piece wheels.